Dial pulse restorer



Jul 25, 1961 G. M- ANDERsoN DAL PULS RST0RER 2 SheetsSheet 1 Fi1ed June 6, 1957 July 25, 1961 G. M. ANDERsoN 2,993,960

DAL PULSE RBSToRE:R

tn1tej StateS Patent 2 ,993,9o DIAL fULSE RESToRER Geofge M. A1ldefson, vvhippany, NJ., oSsigfof fo McGfaW-Edison compony, E1gin, 11L, o oofpofofion of De1owofe ed June o, 1957, Sef. No. oo3,974 2 ClaimSl (cL 1791o) This invention felates to appafatuS fof enabling a te1e ohooe SubScfibef to Inake connection betwoen his Station equlpfnent and a fen1ote dictating Inaohine by a dialing opefation and to thefeupon contfo1 the Iflachine by fuf thef selective dialing opefations, and o1ofe pafticulafly the invention felateS to n1othodS and appafatuS fof detect ing the difforential Sufges of ofigina1 dial po1Ses Which appeaf i11 coInpleted voioe ffequency telephone lineS and fof pfoducing thefe pulSeS coffeS1)onding to the ofigina1 dial pulSes to enable a )oSitive and dependable contfol of the dictating n1achine.

In the pfeSent deScliptiofI the teffn D.C. 1)I11Se is usod With fefefence to pulseS chafactofized aS having a subStantially stable n1agnitude fof a tifI1e dufation, and the tefn1 sufge is uSed with fefefence t() pnlSeS ohafactefized aS being Shafply vafiab1e thfoughout theif tiIne dufation.

In telephone appafatuS difect ouffent li11es afe pfovided betvvee1 Subscfibefs, StationS and the centfal station so that the dial pulSes oan opefate the Svitohing felayS as telephono nuIflbefs afe dialed. fIovvevef, thefe is intefposed an isolating tfansfofoef of oondensef betvveen the voice ffeqUency lineS of the fespectiVo subScfibefs, Statio11S. It iS desifable When a dictating nlaohine is added fo a telephone syStefn that it be connected in place of a Standafd subscfibef,S station So that efficient utilization iS n1ado of the telephone lines and switohing appafatuS. Such dictating n1achine n111St -be contfolled as to staft Stop, indeXing, playback, etc. ThiS is done by selectivelyopefable Stepping felayS contfoned by dial pulSes ffoIT1the subScfibef,S Station as pfe-Selected n-UInbefs afe diaIed, Howevef, the D.C. dial p111SeS at the subScfibef,S station afe diffefentiated by the line tfansfofn1ef of condensef to pfoduce only n1oInentafy SufgeS of onffent i11 the con1 pleted telephone line vvhefo the dictating f1achine is con nected. Tefe iS a paif of theSe n1omentafy Snfges fof each ofiginal dia1 pI11Sea sufge of one olafity at the leading edge of the pulSe and a sufge of opposite polafity at the tfailing edge. T11eSe momentafy SufgeS do not contain su0cient enefgy to enable feliable opefation of the contfo1 felays of the dictating Inachine. By the pfese lt invention an equipnlent iS pfovided at tho calIed sta tlon capable of deteoting the diifefentiated snfgeS of ofig inal dia1 pulSeS and of tfiggefing a n1eans fof thefe pfo dllcing 1).(:. polSes coffeSponding to the ofigina1 pI11ses.

An objecf of oly invention is to Pfovide iInpfoved ap pa atoS fof feliably contfoning dictating InachineS ovef voloe ffequency lines of telephone systeffls in feSponse to D.C. p111Ses pfoduced by Seleotive dialing of nnn1befs at a Subscfibef,S station.

The pfesent invention iS in an electfonio equipInent Which iS capablo of diStingUiShing bet een a dial pulSe at the dictatof,S Station afld all othef electfical ouffentS Whethef voice cuffents, noise, of othef SignalSand Which When it SenseS a dia1 pulSe at tho subScfibef,S Statiof1 Will pfodUce an equivalent ]).(Z. pulso fof contfolling the dio tating Iflaohine.

Dial pulSeS of telephone equipInent have chafactefiS ticany a many timeS gfeatef magoitude than that of the speech signals and occnf at a ffequency of about pef Second dIlfing the fetufn of a dial to home poSition; howevef, the dI1fation of individ11al pulses IT1ay vafy vvidely ffom aboot 35 Ins. to a fnaxiInum of abont 80 to 90 ms.

Anothef obiect of o1y invontion iS to pfovide a dial lCe pulSe festofef Which is fesponSive only to the diffefen tiated SufgeS of fespective dial pulSeS occuffing within a tiffle intefval not leSS than the IniniIn11fn noffTal dufation of Standafd dial pulseS nof gfeatef than the naxiolnff1 dufation thefeof.

Anothof obiect iS fo pfovide such festofing eqnipment which iS adapted to fespond only to voltage Sufges of a fflagnitude substantially gTeatef than that of the speech ffequenoy conlponents.

These and othef obiectS and featufeS of fny invention Will be appafent ffofI1 f11e folloWing desofiption and the appended `o1aimS.

In the desofiption of IT1y invention fefofence is had to the accompanying dfaWingS, of Which= FIGURE 1 is a Schenlatic cifcuit diagfam of a combinatioI1 telephone-dictation SySten1 Showing a dial pulse festofef accofding to n1y inventio11;

FIGURE 2 is a cuTve showin a series of DC. dial pUlSes;

FIGURE 3 iS a curve showin the diierentiated voltage SUfgeS of succeSSive dial pulses Such aS afe fed to the dial I)11lSe festofef of nly invention; and

FIGURE 4 is a chaTt showin the tiIne relation of si nificant voltageS and powef levels appoafing at tho SuccesSive points in the dial pulse festofing cifouit.

In FIGURE 1 a standaTd SubcribeT,S tele hone station 10 of the dial type is connected thfongh a D.C. oifcuit 11 to a centfal station 12 having tho IlSIlal SWitching appafa t11S feSponSive to the diol p11SeS ffom the Subsofibof,s

Station fof o1a1ing connection to Selected s11bScfibefs,

lines. tJpon The caning pafty dialing the nufnbef aSSignod to tho station whefeat a dictating Inachifle 13 iS looated, connection is Inade thfoI1gh a foSpective isoloting oon denSef of ffansfofII1efa tfansfoffIlef being Shovvn by vVay of exaInp1eto a coffesponding voice ffequency lino 15. T his liIle iS nofInally held open by a sWitoh1o, bot opon feceipt of finging cuffent a felay 17 connecte(f acfoSS the line thfough condensef 18, feSiStof 19 and fectifief 20 is opefated to cloSe the owitch 16 aS WeH os to open a Second sWitch 21 11efeinaftef oxplained. Tffo c1os ing of svvitch 15 cofnpletes connection of the felay 17 acf()SS the line though an inductof 22 to cauSo the fe1ay to be held opefated by the cuffent in the 1ine, and it cofnpletes also connection of the caHing pafty thfough. the 1ine tfanSfofn1ef to the dictating machine 13. Acfoss the cifonit 15 at the faf Side of the sWitch 16 is on RL tefn1inating iInpedance 23. Also, the pfinlafy of a tfonsfofn1ef 24 iS conneoted aofosS the 1ine at fhis point thfough an 1( ifnpedance 25, TiS tfanSfofmef feedS thfoogh a low-pass 1iltef 2o and an output cifcuit 27- gfoonded at one end at 28 to the dial pulso feStofef of n y invention indicated at 29. Fof feaSons vvhioh vvi11 appoaf, the faf1S fofmef is con1ected to eect a phase fevefsa1 of the cuffentS fed to tho dial pulse feStofof.

Dial )]JlSes pfoduced at the subScfibof,S Statio11 Whon a nUnlbef is dialed appeaf appfoxin1ately as indicated at 30 in FIGURE 2. As iS vvell known, on dialing 1111Inbef 1 of lettefS AB(:, a single p111Se of aboIlt 40 n1Si is pfoduced; on dialing nun1bef 2 of lettefs DEF, tWo such pI11SeS afe pfodnced at intefva1S of about .1 Second, etc. Howevef, fhe iSolatiog tfanSfof1ef 14 paSSeS only tho diffefentialS of theSe dial pulSes vvhich appeaf as sufgeS at the leading and tfailing edgo of each polse. Sinco theso Sufges undefgo a phase fevefsal vvhen fed thfongh tho coupling tfansfofff1ef 24, thefe is a negative Sufge 31 at each 1eading edge of a dial polse and a poSitive Sufgo 32 at each tTailin ed e thereof as shown in FIGURE 3.

The input cifcuit 27 to the festofef iS connected to tho cathode of a tube 33 opefating as a fectifief. ThiS cathodo is biaSed poSitively by about 15 volts by IneanS of a bleedef cifcuit including feSiStofs 34 and 35 conoected bo tween B and gfound. Tho plate of this tube iS con Pafented Jul 25, 1961 nected to B thfough a high feSiStance 36 of about 3 Inegohms, but iS nofmany held positive by only a sfna11 vo1tage becauSe of itS being diectly con11ected to tho gfid of an e1ectfon tube 38 opeTating in connection vyith a Succeeding tt1be 39 as a I1l11tivibfator. Since fhe plate potentia1 on the tube 33 iS thuS held negative vvith fespect to the cathode potenfiaL the fube iS nofInally in a blocked condition. Thus, on1y an inpUt vo1fage of negafive SigI1 and of a n1agnitude greater thaI1 the cathode biaS vi11 Tender the tube conductive. The 1eading differentia1 surge of a dial p111Se IIleefs both of theSe conditionS to cauSe the i11 )I1t tube 33 to be tfiggefed info a conductive condition.

vVhen the tube 33 iS Tendefed conductive, itS plate is dTavn negative fo Teduce the glid voltage on the tUbe 38 fo negative valueS and to p1ace this tube in a b1ocked condition- The p1ate of tube 38 iS connected to B throngh fesiStol 40 and iS connected a1So to the grid of tI1be 39 throUgh fesistor 41. T11e p1ate of tube 39 is connected to B thfoUgh fesiStor 43 bUt fhe cathode of thiS tIbe iS biased heavily posifive to fendef the fube nofTnany b1ocked, the biaSing being effected by a b1eedef oifcuit including feSistors 43 and 44 connected betvveen B and gTound. when the tube 38 becoIneS b1ocked itS plate potential iS incfeased to incTeaSe the gTid vo1tage of tube 39 su8icienfly to fendef thiS t11be conduotive. AS Soon as tube 39 Staffs this conductance itS p1ate vo1tage iS Te duced to cauSe a voltage to be fed back thfough condenSef 45 to futther increaSe n1on1entaril the ne ative volta e on the gTid of tube 38 and to charge fhe condenSeT. But as the negative charge on the condenSer 43 1eakS off thTough fesisto1 36, the tnbes 38 and 39 aTe Testored to theif initia1 conditionS, Which aTe a conducting condition fo1 the tube 38 and a non-condncting condition fo1 the tube 39, The tin1e conSfant of the condonsef 43 and 1eSiSto1 36 iS Such that this reStofation oconTS in abont 33 n^1S. aftef the instant the input tube 33 vvaS ffiggefed into a condUctive condition. n eect therefofe of feeding a Inon1enfaTy negative sI11ge to the inpnt tube 33 is to Tendef the tnbe 39 conducting fol a period of about 33 InS.-vhioh iS a period considefed aS being the T1iniI1I1T1 ti1Tle dnfation for any standaTd dia1 pulSe.

Fo11oving the n1Ultivibfatof 3839 iS an electTonic tube 46 having itS cathode gTounded, itS gfid oonnected though high TeSiStof 47 of about 6 megohms to B and its p1ate connected thfoUgh resistof 48 to B Tho gfid of this tube is thefefofe he1d poSitive to TendeI the tube nofola11y conductive. The gTid iS howevef connected fhough TesiSto1 49 and condenSef 30 fo the plate of the n1111tivibTatof tube 38. vv11en at the end of the 33-n1S, pefiod aboven1entioned the tube 38 is feStofed to condUctive condition, its p1ate voltage is sbifted negative fo pI111 the gTid of the tnbe 46 negative though the cifcuit 4930 and to fendef the tube 46 non-conducting. The tine fof the chafge on condenSef 30 to 1eak o1f thTongh the high feSisto1 47 iS Set at about 70 Ins. T11US, the tube 46 iS he1d in a non-condncting condition for a pefiod of about 70 n1s. Sfafting aftef a delay of aboUt 33 1T1S- ffoIn the instant the inpnt tUbe was tfiggefed by the leading diffeT- entia1 Sufge of a dia1 pI11Se Fonowing the tube 46 is a IT1L11tigfid detector tube 31 having itS cathode connected thfough TeSiStof 32 to gTound, its 11fSt gTid con11ected to the inpnt 1ine Z,7 itS second gTid and plafe connected thfongh Tespective fesiStors 33 and 34 to B and itS t11ifd gfid connected fhongh TesistofS 33 and 36 to gTound and thfough TesiStor 33 and condenSef 37 to the p1ate of the pTeceding tube 46. During the 70-IT1spefiod when the tube 46 is non conducting, itS plate pofentia1 fs increaSed to place a poSi tive potential on the grid 3 of tube 31. If now a oSitive diffefentia1 sufge iS fed fo grid 1 Whi1e gfid 3 is held poSi five, t11e tube 31 is p1aced in a condnctive state, 1t We11 theTefore appea T that the tube 31 iS 11ti1iZed as an e1ectonic gate foI SenSing Whenever a negative SuTge fed into fhe fopnt tube 33 of the reStofe iS fonowed not 1eSS than 33 o1S, lateT noT InoIe than 103 n1S. 1atef by a poSitive SI1fge.

4 A dial pu1Se of a dufatioI1 between theSe tin1e limifs Wi11 theTefofe triggef the tube 31 to fendef it conductive.

A momentaTy oonductivity of tube 31 tfigge1S a fou16 vibTato1 including tubeS 38 and 39. T1Je tube 38 haS its cathode gTounded, itS gTid connected thfough condenSef 60 to the plate of fube 31 and a1so through a high TeSiStor 61 of about 1 Inegohn1 to B as We11 as thfough a condenSer 63 fo the p1ate of tube 39, and has ifS plate con necte(1through a fesiStoT 63 to the cathode of tube 39 and onwaTdly through a TeSistor 64 to B The cathode of the tube 39 1S alSo connected thTough bias 1eSiSfof 63 pafalleled by condenSer 66 to gfound, and the plate of this tube is connected alSo throngh feSistor 67 and co11 of felay 68 in pafa]1e1 With condenser 69 to B Re- SiSfofS 64 and 63 form a bleeder cifcuit betWeen B and gToUnd fof Supp1ying poSitive voltage fo the plate of tube 38, Since the tube 38 haS its gfi(1 held poSitive but by 1esse1 vo1fage, the tube is nofn1ally in a conductive State to pfoduce a voltage dfop acfoss the TeSiStof 63 the effect of Which iS to hold the gd of tube 39 negative with fe spect to its cathode and to Tendef thiS t11be nofIna11y non conductive, vvhen the tube 31 is fendefed conductive ifs p1afe volfage fa11s to UH the gTid of tube 38 negative thfough the coupling condenSef 60 and to fender this tube noncondUcting. AS the tube 38 iS Tendefed nonconducting, its p1ate voltage TiSeS to fender tnbe 39 conducting and to opefate the fe1ay 68. As soon as the t1be 39 begins condncting, itS p1ate vo1tage is feduced to feed back a voltage through condenSer 62 to kee the gfid of tube 38 negative whereby fo pfolong fhe pefiod over vhich tube 39 iS ke t conducting and the felay is kept Opefated. vhen the chafge on the condenSef 6Z haS 1eaked off throngh the high resistor 61, the tubeS 38 and 39 aTe fe Sfofed fo theif initia1 conditionS to cauSe the Telay 68 fo dTop ol1t. The tiIning of the feSistof 61 and condenSef 63 is Set at about 30 Ins. ThuS, When the detecfof fube 31 is InoInentafily Tendefed conductive by the siInulfaneous app1ication of positive voltageS on both itS gfid 1 and gTid 3, a DCL pu1Se iS fed through the fe1ay 68 fo ho1d it opefated for about 30 IT1s. T11is InoInenfary opefation of the Te1ay feSponSive to tho detection of a dia1pu1se opens a contTo1 cifcuit 70 the San1e aS fhe pulSing Svitch opens the fe1e hone 1ine at the subScfibef,S Station. T,he oifouit 70 iS connected to a contro1 appafafuS inc1nding a SefieS of Stepping fe1ays fof oontToning the dictating nachine bnt which need not be hefein deScTibed fof the purposeS of the pfeSenf invention.

Te table in FIGURE 4 shows the felative tin1in of critica1 voltageS and povvef leve1S in the pu1Se reStofer upon a negafive di1ferentia1 SuTge 73 being fed to fhe Testofef fonowed by a poSitive suTge 74 Within a time interval greateI than aboUt 33 IT1S. and 1eSS thaI1 about 100 n1s., aS indicated by the curve A. The negative surge 73 fendefS the tube 33 InoIIlentafily conductive as indi cafed at 73 of cufve B. T1is InoIIlentary conduction of tube 33 caUSes the g1id of tube 38 fo be Shifte(1 negative on an 1C discharge cuFe for a peTiod of abont 33 n1S. aS indicated at 76 of curve C. Dufing this Sanle pefiod tho grid of tube 39 iS 11e1d poSitive at a Substantiany 6xed value aS indicated at 77 of curve D Starting With the Tetnfn of the grid of tube 39 to nofn1a1 value the gfid of tube 46 iS Shifte(1 negative on an RC discharge cufve over a pefiod of about 70 InSl aS indicated at 78 of curve E. DuTing thfs period the g1 id 3 of tube 31 iS he1d poSi tive at a Substantia11y fixed value aS indicated at 79 of curve F. vvithin this tiIne interval the rid 1 of tube 31 iS Shifted n1omentafi1y positive aS indicated at 74 of cUTve 1 1. The fesu1tant coincident app1ication of positive vo1tages oI1 both gr1ds 1 and 3 of tube 31 oaUSes this tube to be n1onTentafily conductive as indicated at 80 of ourve G. The momentary oonductivity of tube 31 shifts the grid of tube 38 negative on an RC d1Schafge curve over a pefiod of about 30 1118. as indicated at 81 of cufve II to Tender the fube 38 conductivo over fhiS tiIne intervaL This oaUSes the grid of tube 39Which iS norn1ally fleld I1egativoto be shifted to a substantial ly zero value fof the dI1ration of this Ins, intefva1 aS indicated at 82 of cUfve 1 and this in tnTn ca11Ses the olltpllt Telay 68 to be he1d operated thTougho11t the SaIne S0-n1S. intefva1.

It wi11 be observed that the pfesent dial pulSe restoTef is Sign-se11Sitive siI1ce the input tube reSponds only to SIIrges of negative Polarity coffeSponding to the leading diffefentialS of Tigina1 dia1 po1SeS, and the detectoT tube 51 TespondS only When each SuTge of negative polarity iS foHowed by a surge of po3itive po1aTity coTTesponding to the trai1ing diifeTential of an oTiginal dia1 pnlSe. AlS(), the input tube is biaSed to SeTve as an ampHtude diS cTin1inatof so that only the lafge diffefential SUTgeS of dia1 pu1SeSwhich aTe typically aboUt 0ve to ten tin1es greater than the n1agnitude of the londeSt speech Signa1S aTe effective to oPefate the pulse TestoTer. Sti11 fllrther, Since the 1eading diffefentia1 suTge iS L1tiliZed to pfoduce a positive voltage on grid 3 of the detecto fLlbe 51 at a delayed tin1e equal to the nliniInuTn dllTation of oTiginal dial pulses and thiS positive voltage on grid 3 iS then Inaintained fo1 a duration equa1 to the InaXinuIn t()1erance of tiTne duration of the oTigiI1a1 pulSes, t11e tnbe E1 iS 11tiliZed as o coincidence detectof fequiTing that te tiIIle duTation of the original pulseS II111st be vvithin pfe- Scribed liII1itS in ofdeI to opeTate the pu1Se feStorer.

The ffequencieS vhich Inake Up the diffeTontial SuTgeS of origina1 dial plllseS 1ie in a lower frequency band princiPa11y below 100 clp.S. but containng St11 subStaT1- tia1 eneTgy components I1p to 1000 c. ).S. 1f deSifed, a diScIin1ination in favoT of the f,eq1ency con1ponentS of the diffeTentia1 SurgeS of the dial pu1SeS and againSt the speech fTequency coInponentS IIlay be obtained by inter posing the afofen1entioned lovV-pass filter 26 betvveen the te1ephone 1i11e 15 and the festofer 20.

Whenever the dictator hangS up hiS handset and thereby openS the telephone line to his telephone Station, the relay 17 is dropped out to diSconnect the dictating n1a chine 13 and dia1 pulSe TeStofeT 29 ffoIn the telephono 1i1e. Also, as the felay dfopS out it closeS the svVitch 21 to connect a low TeSiStof 72 of about on1y 100 ohms ffoIn cathode of tube 50 to gfonnd ThiS So feduces the p1ate vo1tage of the preceding tube 58 that thiS tube iS Tendefed nonconducting. vVhen thiS ttlbe is Tenderod nonconducting the tube 50 1oses itS gtid biaS fToIn the TesiStor o3 to TendeT thiS tobe conducting and to cause the e1ay o8 to be he1d opeTatedl This holds the con tro1 cifcuit 70 openvvhich iS the condition for placing the dictating n1achine in a neutral coIlditio11. vice vefsa, aS Soo1 as a SubScriber dialS the 1ine to Which the dictat ing I1achine is connected, the TeSI11tant opening of the Switch 21 causes the Telay 68 to drop ont and the ciTcuit 70 to be he1d c1osed except When dial pI11Ses are detected by the dial pu1Se TeStoTer.

without inteIlding any nnnecessary lin1itation thefeto, the fo11ovving typica1 valueS of the conlponents of the festorer may be noted, Whefe Tesistors aTe designated by The pafticular embodinlent of my invention herein Shown and deScfibed is intended to be inuStrative and not liII1itative of Iny inventioI1 Since the San1e is subject to changes and Inodifications Without depaTture from the scope of ITly invention Which I endeavor to expresS according to the fonowing clailTIS.

1 claiIn:

1. An a pafatus for detecting iI1 con1 leted telephone ciTcuifs the oppoSitely polafized diffefential SUrgeS of oTiginal dia1 pulSes at a calling station and for foTIning feSpective 1).C. pulSes in TesponSe thefeto Said ofiginal pu1SeS being characterized as having a time duration vaTiable betvveen predetern1ined liInits, compriSing an electronic gate ciTcuit Tequifing tvo control voltageS ap- )1ied siInultaneouSly thereto to open the Sane; neanS for producing Said tvvo contro1 voltages Tespo11Sive Tespective 1y to fhe leading and trailing differentia1 SuTgeS of said original dial p111Ses inclIlding Sign-SenSe detecting nTeans TesponSive on1y to suTges of opposite polarity occurTing in the Sequence of that of Said leading and trailing diffefential SorgeS, aInpHtude-discriIninating Ineans for Tendefing Said detecting nleans responsive on1y to SurgeS of a IT1agnitude subStantially greatef than the peak voice Signa1S in the telephone line, and ti1ing Ineans for de- 1aying the fist of said contro1 voltages fo1 the tiIne of n1inin1un1 duration of Said origina1 pulseS and fo1 nlaintaining Said first contm1 vo1tage for a dufation equa1 to the maximum variatio11 i11 tin1e dufatfon of Said origina1 1)I11SeS vvhereby a detection of aI1 original dial p111se canSes said tvo control voltageS to occI11 coincidentally to open said gate circuit; and n1eans TeSponsive to each Inon1entaTy opening of said gate circuit for poducing a D.C. pu1Se having a tin1e duration 1onge1- than the IIliniInum duation of said ofiginal pulses and shorteI than the Inaximuo1 duTation thereof.

Z. Te appaTatuS Set forth in claim 1 inc111ding a loW- paSS 1ilteI i11 the tTanso1iSSion cifcuit betvveen the ap paTatuS and the telephone ciTcllit foI discrin1iIlating in favor of the diffefential s11TgeS of dial pulSeS and agai11st the higher ffequency Speech oo11ponents i1 the tolephono circ11it.

Iefeences (:ffed i11 the fi1e of t11is patent UNITED STATES PATENTS Z,S04,976 GTieg Apr. ZS 19S0 Z,S77,8Z7 Ton1pkins Deo. 11, 1951 z,634 346 Hoeppner Apr. 7 193 2 791 633 .Tones et a1, May 7, 1907 

